1. Field of Art;
The present invention relates to a lithium battery including an amorphous cathode active material mainly composed of vanadium pentoxide (V.sub.2 O.sub.5), which is small-sized and has a large charge-discharge capacity. More particularly, it relates to a rechargeable lithium battery comprising an anode active material made of metallic lithium or a lithium alloy, an amorphous cathode active material prepared by adding V.sub.2 O.sub.5 with at least one metal oxide selected from the group consisting of P.sub.2 O.sub.5, TeO.sub.2, GeO.sub.2, Sb.sub.2 O.sub.3, Bi.sub.2 O.sub.3 and B.sub.2 O.sub.3 and/or at least one metal oxide selected from the group consisting of MoO.sub.3 and WO.sub.3, and an electrolyte.
2. Related Art Statement;
Many proposals have hitherto been made to provide a high energy density battery in which lithium is used as the anode active material. For example, a battery wherein an intercalation compound of grahite and fluorine is used as the cathode active material and metallic lithium is used as the anode active material has been known by the specification of U.S. Pat. No. 3,514,337. A lithium battery including graphite fluoride as the cathode active material and a lithium battery including manganese dioxide as the cathode active material have already been sold commercially. However, these known batteries are primary batteries which are not rechargeable.
The specification of U.S. Pat. No. 4,009,052 discloses secondary batteries wherein lithium is used as the anode active material and sulfides, selenides and tellurides of titanium, zirconium, hafnium, niobium, tantalum and vanadium are used as the cathode active material; and secondary batteries wherein lithium is used as the anode active material and chromium oxide or niobium selenide is used as the cathode active material are proposed by J. Electrochem. Soc., 124(7), 968 and 325, (1977). However, these batteries are not satisfactory in their performance characteristics and from the economical standpoint of view.
Lithium batteries having amorphous cathode active materials of MoS.sub.2, MoS.sub.3 and V.sub.2 S.sub.5 are known by J. Electroanal. Chem. 118, 229 (1981), and lithium battery having an amorphous cathode active material of LiV.sub.3 O.sub.8 is known by J. Non-Crystalline solids, 44, 297 (1981). However, these known batteries have problems in rate capability and are inferior in charge-discharge characteristics. The use of crystalline V.sub.2 O.sub.5 as the cathode active material has been proposed by J. Electrochem. Soc. Meeting (Toronto, May 11 to 16, 1975, No. 27). However, the battery prepared in accordance with the proposal has a small capacity and is unsatisfactory in charge-discharge characteristics.
A solid solution of V.sub.2 O.sub.5 and P.sub.2 O.sub.5 is disclosed in Japanese Patent Laid-Open Publication No. 134561/1984 which was laid open to the public on Aug. 2, 1984. However, the solid solution was prepared by quenching the molten mass in air and had some problem in reproducibility of the performance characteristics of the battery using the same. Moreover, the solid solution was not fully amorphous since the quenching rate was low. French Patent Laid-Open Publication No. 2527842 (laid open to the public on Dec. 2, 1983) as well as DT-OS No. 3319987 (laid open to the public on Dec. 1, 1983) which are the publications of the patent application by Western Electric Company Incorporation, disclose a lithium cell comprising a nonaqueous electrolyte and a cathode made of a crystalline composite metal oxide material containing V.sub.2 O.sub.5. A further known literature is a report by ourselves, which is published by Journal of the Electrochemical Society, vol. 132, No. 2, pp 512 to 513 (1985) under the title of "V.sub.2 O.sub.5 --P.sub.2 O.sub.5 Glasses as Cathode for Lithium Secondary Battery".